This invention relates to an inertial barrier system for attenuating the energy of errant vehicles.
It is well known that many obstructions located next to the roadbeds of highways create safety hazards. These obstructions take the form of overpass support columns, bridge abutments, guardrails, road signs, railings, and the like. Since the existence of these hazards have been recognized, a continuous effort is being made to provide suitable energy attenuation devices in front of the obstructions, in the potential path of travel of an errant vehicle, in an effort to substantially reduce damage to the vehicles and personal injury to the passengers.
Prior devices which use sand or other forms of readily dispersible particulate material as the energy-attenuating medium, for placement before roadbed articles, are shown in U.S. Pat. No. 3,606,258 to J. C. Fitch, entitled "Energy Absorbing Deceleration Barrier". Another type of energy-attenuation device using sand or other dispersible particulate material is disclosed in U.S. Pat. No. 4,073,482 issued to Wan Seegmiller and Bruce O. Young, entitled "Inertial Barrier System". The inertial barrier system of the present invention is a modification or improvement of the barrier systems described in these foregoing U.S. patents.
For example, these foregoing patents discuss the problem of "ramping" of an errant vehicle, i.e. the tendency of the vehicle to rise over an energy-attenuation system and overturn, due to the accumulation of debris below the center of gravity of the vehicle. These patents also generally discuss the opposite problem of "nose diving", where the vehicle tends to flip because the front is forced down. The wellknown technique for minimizing ramping or nose diving is to locate the center of gravity of the dispersible energy absorbing mass essentially in a direct line with the average center of gravity of the moving vehicle; for example, approximately 22-25 inches above the road surface. This location of the mass center of gravity tends to eliminate the development of a force couple which would ramp or nose dive the errant vehicle. The inertial barrier system in accordance with the present invention incorporates this feature of preventing ramping or nose diving by elevating the center of gravity of the mass essentially in line with the average center of gravity of the errant vehicle.
The foregoing U.S. Pat. No. 4,073,482 also describes a system which minimizes environmental degradation of the system, due to the prolonged effects of roadside vibrations and the like. This degradation of the system is also precluded by the present invention. To accomplish this feature, the present system substantially eliminates the possibility of shifting of the dispersible matter downwardly, and the resulting undesirable lowering of the center of gravity of the dispersible mass below the designed center of gravity for the system.
Further, the present energy attenuation system precludes degradation by providing containers which receive a mass of dispersible energy-attenuating material, such as sand, continuously throughout the entire container height. This design eliminates the interposition of lightweight module components between the major portion of the dispersible mass and the support surface, which has been found to cause undesirable movement or "walking" of the container and a downward shifting of the mass.
In addition, the present invention accomplishes the foregoing advantages in a manner which reduces the number of component parts of the system. In one form of the system, for example, the number of component parts of each module is reduced to two, including a protective covering lid. In addition to the economical advantages resulting from a reduction of component parts, the present invention thereby provides a reduced amount of material that might be dispersed, upon impact by an errant vehicle, into traffic lanes, where it could cause a secondary accident.
In addition, this invention enhances the functional operation of the inertial barrier modules by providing each module with a substantial void in its lower portion which assists in properly elevating the center of gravity of the mass. Also, the void allows the dispersion of a portion of the sand or other dispersible mass contained in the module into the void, upon the initial impact by the errant vehicle. This initial transfer of a portion of the mass into the void permits earlier dispersion of the mass, and tends to lower the peak stopping force applied to the errant vehicle by the module. This feature also provides a more uniform `G` load on the vehicle, by allowing the mass to disperse almost immediately upon impact, rather than having substantial dispersal await the fracture of all wall portions of the module. Additionally, the interior of each module in accordance with this invention is shaped to tend to project a portion of the mass vertically when impact occurs. This vertical component of mass distribution also ameliorates the peak of `G` load applied to the impacting vehicle by the modules.
Briefly, the above-described features and advantages of the present invention are accomplished by an inertial barrier system which provides at least one module. The module defines a frangible container having a generally inverted U-shaped type configuration. The container wall portions are preferably integral, to provide a leakproof container for a dispersible mass such as sand. The upper portion of the container is enlarged and opened, to receive the dispersible mass. The lower portion of the container has a substantially reduced cross-sectional area, and defines a central void of substantial volume. Preferably, this void is circular or cylindrical in configuration, and is defined by annular portions of the container which extend downwardly to the supporting surface.
The upper and lower portions of the container cooperate to receive a dispersible mass such as sand continuously throughout the entire container height. The container also maintains the mass in a manner which elevates the center of gravity of the mass into the enlarged upper portion. The void in the lower portion assures that the center of the gravity of the mass is so elevated. The void also is adapted to receive a portion of the mass as it is dispersed upon impact. A container cover, preferably made from plastic material, is fitted over the top of each container.